Japanese laid-open patent publication No. 2004-299036 discloses an electric hammer having a dynamic vibration reducer which forms a vibration reducing mechanism. In this hammer, a weight of the dynamic vibration reducer is actively driven by utilizing the pressure within the crank chamber, so that vibration caused during hammering operation can be reduced.
Further, Japanese laid-open patent publication No. 2004-216484 discloses an electric hammer having a counter weight which forms a vibration reducing mechanism. In this hammer, the counter weight is driven via a crank mechanism that converts the rotating output of the electric motor into linear motion, and it serves to reduce vibration caused in the hammer during hammering operation. However, further device improvement is desired in both of these known vibration reducing techniques.